Support forms are known in the prior art to provide an envelope or enclosure for a pourable settable material as it hardens into a structural base support for flagpoles, basketball backboards, fences and the like. The pole or other structural element has a first end thereof positioned within the confines of the form and the second end of the structural element extends out of the form. Thereafter, the pourable material is then added to the support form which, once it hardens around the first end of the structural element, forms a rigid, integral structure therewith.
For underground applications, that is, in applications in which the support is placed either partially or wholly beneath ground level, a number of problems exist in known prior art apparatuses. First, conventional support forms such as SONATUBE.TM. are shaped so as to have a relatively constant cross-section along the length of the form. Forms having this geometry, when positioned either partially or wholly below ground level, are subject to tipping or leaning as a result of settling or frost heaving, that is the upthrust of ground which occurs due to the freezing of the soil, typically seen in the colder climates during the winter months. The net effect of the shifting ground against or adjacent a form of relatively constant cross-section along its length is that the form, and the structural element encased therein, either tilts to a side or is pushed toward the surface thus degrading the structural capacity for which the support was intended.
A second problem which occurs in conventional forms of this type is that as the material is poured into the confines of the form, after the form has been positioned within the hole, the pourable material tends to seep between the bottom of the form and the ground and tends to push or lift at least a portion of the form toward ground level. This seepage may occur unevenly so as to tip or tilt the support to one side.
Wherefore, it is an object of the present invention to provide a support form having a cross-sectional design which lessens the effects of frost heaving to produce thereby a more sturdy support which will not degrade during the change of seasons.
A further object of the invention is to provide a support form having an annular anchoring means to allow the form to seat properly prior to and while pourable material is being poured into the form and to minimize shifting, tipping or leaning caused by frost and/or other environmental factors.
A still further object of the present invention is to provide a form having a design which facilitates the storage of a plurality of forms, prior to use, by allowing them to nest one within the another.